| As a traditional dish of Miao and Dong ethnic groups in China,sour soup fish is cooked with fresh fish and Guizhou specialty sour soup as raw materials.Traditional sour soup fish is mostly sold in local restaurants,and industrial products in the market are still blank.Low-acid leisure retort pouch food products with a certain shelf life need to be sterilized at high temperature after vacuum packaging,which will damage the texture and color of fish fillets.Sour soup itself has sour and refreshing taste,it will become acidified food,and then the sterilization strength will be greatly reduced if its pH value is controlled below 4.6 through technological research.Thus,this study will systematically analyze the acidification technology and sterilization technology of channel catfish,and analyze the quality changes of sterilized fish fillets under different storage conditions,in order to provide theoretical guidance for the industrial production of sour soup channel catfish.1.The effect of static pickling technology on pickling rate of channel catfish fillets was studied.The best sugar-acid ratio of the pickling solution was determined through sensory evaluation by using pre-dried channel catfish fillets as raw materials and conditioned Kaili red sour soup as pickling solution.On the basis of the best sugar-acid ratio,the effects of initial total acid content,liquid-material ratio,fillet thickness and pickling time on the acidification rate of channel catfish fillets were analyzed.The results showed that the sensory score of pickled fish fillets in pickling solution with sugar-acid ratio of 4:1 was the highest.When the ratio of liquid to material was 2:1(w/w),3 mm thick fish fillets could be acidified when pickled in 25 g/kg sour soup for 12 h.Increasing the initial total acid content of pickling solution could significantly improve the pickling rate,and increasing the liquid-material ratio could improve the pickling rate in the later stage of pickling.The pickling rate of thicker fish fillets was slower in the early stage of pickling,and the pickling rate in the later stage was almost the same as that of thin fish fillets.Through Box-Behnken test,a prediction model of fish fillet acidification with pH value as response value was established,and the verification test showed that the prediction model could predict the pickling process of channel catfish fillets.2.The effect of dynamic pickling technology on pickling rate of channel catfish fillets was studied.The dynamic pickling technology of 9 mm thick channelt catfish fillets was studied by pulsating vacuum and ultrasonic treatment.The results showed that when the vacuum degree of the pickling system reached 100 kPa,there was obvious gas escape phenomenon.The acidification can be completed when the ratio of sugar to acid was 4:1,the ratio of liquid to material was 3:1(w/w),and the pickling temperature was 4?,9 mm thick fish fillets were vacuumized at 100 kPa for 45 s and then vacuum and pickled for 300 min.In the same pickling system,ultrasonic treatment at 420 W every 30 minutes for 5 minutes could also complete pickling in 300 minutes.The pickling time could be shortened to 240 min by vacuum treatment and then ultrasonic treatment.3.The effect of sterilization technology on the quality of channel catfish fillets was studied.Determined the center temperature curve of acidified channel catfish fillets when sterilized at 85?-95?,calculated the sterilization F value,and then determined the safe F value at each sterilization temperature through the heat preservation experiment.Meanwhile,the unacidified fish fillets were sterilized at 110? and 121? as control.The effects of different sterilization temperatures on sensory quality,protein change,water migration and fat oxidation of fish fillets were compared on the premise of reaching the safe F value.The results showed that the acidified fish fillets could reach the commercial sterility state when the sterilization intensity F value reached 5 min,and the unacidified fish fillets could reach the commercial sterility state when the sterilization intensity F value reached 3.6 min.After sterilization,the pH value of the fish fillets decreased slightly,and the total acid content increased slightly.Compared with unacidified fish fillets sterilized at 110? and 121?,sterilization after acidification was beneficial to maintain the sensory quality of fish fillets such as texture,color and smell.The SDS-PAGE electrophoresis band of fish fillets sterilized after acidification was similar to that before sterilization,and the content of TCA soluble peptide was lower and the degree of protein degradation was lower.The cooking loss rate of acidified and sterilized fish fillets was lower,and the loss rate of free water was lower,which was beneficial to maintain water.The effect of sterilization temperature on fat oxidation was not significant.When the acidified fish fillets were sterilized at 91?-95?,the sterilization time could be controlled within 30 min,and the sterilized fish fillets had better quality.4.The stability of channel catfish fillets after acidification and sterilization during storage was studied.The acidified channel catfish fillets were sterilized in a water bath at 95? for 14.1 min(F=5 min),and then stored at 35?,25?,and 4?.The pH value,total acid,total volatile base nitrogen content,texture,color changes of the fish fillets under different storage conditions were determined,and the protein degradation and fat oxidation were analyzed.The results showed that the pH value,total acid and total volatile base nitrogen content of fish fillets were stable during storage.During storage,the elasticity and chewiness changed little,but the hardness increased.When stored at 4?,the shear force increases,and the brightness and whiteness decrease slowly.There was no significant deterioration in sensory quality during the whole storage process.Protein degradation was not significant during storage.Fat was easy to oxidize during storage,and peroxidation value was the main change factor during storage of acidified channel catfish fillets. |
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